Stanford Researchers Test White Roofs and Multi-Hazard Planning as Cities Race to Adapt to Extreme Heat

In Makassar, Indonesia, about 40% of the industrial hub's population lives in informal settlements with corrugated metal roofs, little municipal infrastructure and no air conditioning, leaving residents routinely exposed to temperatures above 90 degrees Fahrenheit. Researchers from Stanford's Doerr School of Sustainability are now painting a couple dozen roofs there with highly reflective white paint, one of the simplest and cheapest tools available for lowering indoor temperatures, in some cases by as much as 5 degrees Fahrenheit.

"Those few degrees can make a big difference," said Rishee Jain, an associate professor of civil and environmental engineering who leads the Makassar project with John Openshaw, a Stanford assistant professor of medicine. When heat and humidity are too high for sweat to evaporate and cool the body, the heart, kidneys and other organs must work harder to compensate, which can worsen conditions such as cardiovascular disease, diabetes and asthma. In Makassar, heat waves are also linked to higher work absenteeism and more cases of dengue fever.

Heat waves are increasing in duration and frequency worldwide, with some regions now enduring 50 more heat-stress days a year than in 1950, and heat wave frequency in major U.S. cities tripling from two events a year to six. Climate scientist Noah Diffenbaugh of the Doerr School said extreme events, especially heat waves, are expected to keep accelerating even if the world succeeds at cutting emissions.

In San Francisco, engineering professor Gregory Deierlein and colleagues are working with the city's Office of Resilience and Capital Planning to build tools that simulate how buildings and residents would fare in earthquakes, heat waves and other hazards, including pilot studies in Chinatown, where many residents over 65 live in older, seismically vulnerable apartments. The goal is to identify building codes and retrofits that address multiple hazards, such as heat and earthquakes, together rather than one at a time.